The presently disclosed subject matter relates to an apparatus and a method for diagnosing a tumor.
Apparatuses for automatically analyzing cells of a subject and providing information related to malignant alteration of the cells are recently being developed. For example, a related art disclosed in WO2006/103920A1 relates to an apparatus for discriminating cancer and atypical cells based on scattered light acquired by light irradiation on a flow cell in which a measurement sample including cells collected from a subject is caused to flow.
Another related art disclosed in JP2013-213690A relates to an information providing method including detecting a level of progress of a tumor based on an N/C ratio (the ratio of the size of a cell nucleus (N) to the size of a cell (C)) in addition to a DNA amount.
A cell goes through a predetermined cycle (cell cycle) of events including DNA replication, chromosome separation, karyokinesis, cytokinesis, etc., whereby the cell divides itself into two cells, each of which returns to the start point of the cycle. In accordance with stages of the cell, the cell cycle can be divided into four phases, i.e. a G1 phase (preparation and inspection phase for entering an S phase), the S phase (DNA synthesis phase), a G2 phase (preparation and inspection phase for entering an M phase), and the M phase (mitosis phase). The cell cycle may be divided into five phases including a G0 phase (quiescence phase) in addition to the four phases. Cell proliferation is stopped in the G0 phase. Each cell is in a stage corresponding to one of the five phases.
When a cell proliferates in accordance with the cell cycle, chromosomes of a nucleus inside the cell also increase. Therefore, when a DNA amount of the cell is measured, it is possible to evaluate which stage of the cell cycle the cell is in. When a histogram of a number of cells for each DNA amount is generated for a normal body tissue, a highest peak of the number of cells generally corresponds to a G0/G1 phase where the DNA amount is smallest. In addition, a second highest peak in the normal body tissue generally corresponds to a G2/M phase where the DNA amount is largest.
On the other hand, each of cells in which DNA aneuploidy has occurred (i.e. each of cells which may be very likely to be altered malignantly) has a greater number of chromosomes. Therefore, the DNA amount of the cell is also greater. Thus, when a histogram is generated for a body tissue including the malignantly altered cells, a peak different from that for a normal tissue appears on the histogram. An analysis apparatus detects the peak corresponding to the DNA aneuploidy to thereby detect the malignantly altered state.
However, due to the influence of the DNA aneuploidy, the number of cells (a ratio) in the S phase cannot be grasped accurately. For this reason, in some cases, detailed information about the tumor may not be able to be grasped.